Gravity and Geodesy - Key terms



ACCELERATION:

A change in velocity over time. The acceleration due to gravity, for instance, is 32 ft. (9.8 m) per second per second, meaning that for every second an object falls, its velocity is increasing as well.

ATMOSPHERE:

In general, an atmosphere is a blanket of gases surrounding a planet. Unless otherwise identified, however, the term refers to the atmosphere of Earth, which consists of nitrogen (78%), oxygen (21%), argon (0.93%), and other substances that include water vapor, carbon dioxide, ozone, and noble gases such as neon, which together comprise 0.07%.

CENTRIFUGAL:

A term describing the tendency of objects in uniform circular motion to move outward, away from the center of the circle. Though the term centrifugal force often is used, it is inertia, rather than force, that causes the object to move outward.

CENTRIPETAL FORCE:

The force that causes an object in uniform circular motion to move inward, toward the center of the circle.

FORCE:

The product of mass multiplied by acceleration.

GEODESY:

An area of geophysics devoted to the measurement of Earth's shape and gravitational field.

GEOID:

A surface of uniform gravitational potential covering the entire Earth at a height equal to sea level.

GEOPHYSICS:

A branch of the earth sciences that combines aspects of geology and physics. Geophysics addresses the planet's physical processes as well as its gravitational, magnetic, and electric properties and the means by which energy is transmitted through its interior.

INERTIA:

The tendency of an object at rest to remain at rest or an object in motion to remain in motion, at a uniform velocity, at a uniform velocity, unless acted upon by some outside force.

MASS:

A measure of inertia, indicating the resistance of an object to a change in itsmotion.

POTENTIAL:

Position in a field, such as a gravitational force field.

SCIENTIFIC METHOD:

A set of principles and procedures for systematic study that includes observation; the formation of hypotheses, theories, and laws; and continual testing and reexamination.

SCIENTIFIC REVOLUTION:

A period of accelerated scientific discovery that completely reshaped the world. Usuallydated from about 1550 to 1700, the Scientific Revolution saw the origination of the scientific method and the introduction of ideas such as the heliocentric (Sun-centered) universe and gravity.

TORQUE:

A force that produces, or tends to produce, rotational motion.

UNIFORM CIRCULAR MOTION:

The motion of an object around the center of a circle in such a manner that speed is constant or unchanging.

VACUUM:

An area devoid of matter, even air.

VELOCITY:

Speed in a certain direction.

WEIGHT:

A measure of the gravitational force on an object. Weight thus would change from planet to planet, whereas mass remains constant throughout the universe. A pound is a unit of weight, whereas a kilogram is a unit of mass.

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